1. Technical Field
This invention relates generally to integrated circuit (IC) packaging technology, and more particularly, to leadless IC packages and related methods of manufacture.
2. Description of Related Art
IC packaging is one of the final stages involved in the fabrication of IC devices. During IC packaging, one or more IC chips are mounted on a package substrate, connected to electrical contacts, and then coated with a molding material comprising an electrical insulator such as epoxy or silicone molding compound. The resulting structure—commonly known as an “IC package”—is then connected to other electrical components, for example, on a printed circuit board (PCB).
In most IC packages, the IC chip is completely covered by the molding material, while the electrical contacts are at least partially exposed so that they can be connected to other electrical components. In other words, the electrical contacts are designed to form electrical connections between the IC chip inside the molding material, and electrical components outside the molding material. One of the most common designs for these electrical contacts is one in which they form “leads” extending out the sides of the molding material. The leads typically are bent downward to form connections with electrical components on a PCB.
Unfortunately, the presence of external leads tends to significantly increase the size of IC packages. For instance, it tends to increase the length and width across the IC packages due to the horizontal extension of the leads. This increased size can be disadvantageous in systems where PCB space is limited. In addition, because the external leads are typically arranged along the sides of the IC packages, the pin count of the IC packages is limited by the linear distance around the IC packages. Additionally, these leads require an additional inspection step for straightness, coplanarity and other required mechanical dimensions (and rework or scrap if they fail the specification). Finally, the leads (starting from the bonding fingers down to the tip of the external portions) add to the total electrical signal length (bond wires+leads), which affect the electrical performance of the IC chip.
Recognizing these and other problems with conventional IC packages, researchers have developed IC packages in which the external leads are replaced by electrical contacts that are covered on top by the molding material, but exposed on the bottom of the IC package so they can be connected to electrical components located beneath the IC package. These IC packages—referred to as “leadless” IC packages—tend to occupy less space compared with conventional IC packages due to the absence of the external leads. In addition, these IC packages eliminate the need for bending the leads to form connections.
Some examples of conventional leadless IC packages are disclosed in related and commonly assigned U.S. Pat. Nos. 6,498,099 and 7,049,177, the respective disclosures of which are hereby incorporated by reference. Among other things, these patents describe and illustrate various design variations for leadless IC packages and various techniques for manufacturing and using the leadless IC packages.